1. Field of the Invention
The present invention generally relates to an improved valve for use in the control of fluids in a pipeline. The valve of the present invention is particularly useful in high pressure pipelines. More specifically, the present invention is directed to a new, novel and non-obvious valve in which the valve components are housed in a cartridge which facilitates repair by permitting quick removal and replacement without requiring that the housing of the valve be removed from the pipeline.
2. Description of Related Art
Ball valves, plug valves and the like are well known to those skilled in the art. A common characteristic of these valves is that they may be moved between their fully open and fully closed positions by quick rotation through an angle of not more than about ninety degrees (90 degrees).
A simple plug valve comprises a rotatable, tapered plug having a bore therethrough disposed in a complementary housing. The plug valve permits fluid flow to be fully stopped by rotating the plug not more than about ninety degrees (90 degrees). However, these valves offer only minimal graduated control of fluid flow achieved by setting the plug at intermediate positions. Further, plug valves require modification for use in high-pressure environments.
A ball valve comprises a rotatable ball having a bore therethrough corresponding to the fluid flow path, together with a seat for sealing with the ball surface. Ball valves operate similarly to the previously described plug valves and offer similar advantages and disadvantages.
Presently lesser known, but offering significant advantages over conventional ball and plug valves, is my hemi-wedge valve described in U.S. Pat. No. 4,962,911, which is hereby incorporated by reference. In short, the hemi-wedge valve includes a curved wedge comprising a tapered, spherical thin section rotatable through the fluid path together with a fixed thrust ball for displacing the distal side of the wedge longitudinally toward the seat as the wedge is rotated between its open and closed positions.
The hemi-wedge comprises a wedge having curved sides so that a first, convex side forms a curved sealing surface with the seat of the valve and a second, concave side forms a curved thrust surface for cooperation with a complementary curved, fixed surface on the thrust ball. An important feature of the hemi-wedge valve is the fact that the thickness of the wedge increases from its leading end to its trailing end. The wedge includes a bore forming a part of the fluid path through its thinner, leading end and is solid at its thicker, trailing end. Rotation of the hemi-wedge through about ninety degrees (90 degrees) into the fluid path gradually closes the fluid path by blocking it with the thicker, solid end of the wedge.
An improvement for use with the hemi-wedge valve described in U.S. Pat. No. 4,962,911 is my valve driver described in U.S. Pat. No. 5,333,834, which is hereby incorporated by reference. This valve driver can turn the rotatable valve member of a ball, plug or hemi-wedge valve. The improved valve driver combines the features and advantages of a conventional free-floating valve element with those of a conventional valve element rigidly connected to an actuator and trunnion. The valve described in U.S. Pat. No. 5,333,834 provides a rotatable valve member which is maintained centered along the actuator axis to avoid cocking while being sufficiently free to float into sealing engagement with the valve seat. These benefits are achieved by loosely holding the rotatable valve member within the yoke or cradle of the valve driver described therein.
One common shortcoming of the foregoing valves is that they do not facilitate quick and easy repair or maintenance in the field. Typically, in order to repair or replace a failed component, e.g., a leaking seat, the entire valve must be removed from a pipeline. Such a repair procedure is generally expensive, time-consuming and often requires disassembly of a portion of the pipeline to completely remove the valve housing and install a new or rebuilt valve. With the valve housing often having been welded or bolted into place, it is necessary to shut down the pipeline, remove the housing, repair or replace the valve, install a new or repaired valve and perform appropriate tests to ensure that the integrity of the pipeline has not been compromised.
Accordingly, there has been a long-felt, but unfulfilled need for an improved valve incorporating an easily replaceable cartridge assembly which may be quickly and easily removed and replaced in a valve body without requiring any cutting of the pipeline. Those skilled in the art have long sought and will appreciate the novel and non-obvious features of the present invention and the improved valve resulting therefrom.
While the invention will be described in connection with the presently preferred embodiment, it will be understood that it is not intended to limit the invention to this embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included in the spirit of the invention and as defined in the appended claims.